Acrylonitrile fibers are in wide use as a fiber for clothing.
A fiber having properties which enable fiber products produced therefrom to be protected from staining, has long been desired, and a number of researches have been made in order to obtain such a fiber. Also in particular fields such as outer clothing and the like, it is desired to endow a fiber with a function which suppresses the infiltration of water (e.g. rainwater) from outside into the fiber.
In order to meet these requirements, it is necessary to develop a technique for imparting water repellency to a fiber.
In order to obtain an acrylonitrile polymer improved in properties as mentioned above, it has been tried to modify acrylonitrile by converting it to various copolymers. Generally, however, it is conducted to subject an acrylonitrile polymer product to a post-treatment with a fluororesin, in order to endow the polymer with water repellency, oil repellency, etc.
As such a fluororesin, many kinds of resins including polyethylene tetrafluoride are disclosed. In particular, a number of fluoropolymer compositions as an agent for treatment of fiber products are disclosed. For example, Japanese Patent Application Kokai (Laid-Open) No. 53-22547 discloses a water-repellent and oil-repellent agent consisting of a copolymer containing at least 40% by weight of a polymerizable compound having a perfluoroalkyl group of 4-16 carbon atoms and 10-60% by weight of vinylidene chloride. Japanese Patent Application Kokai (Laid-Open) No. 51-133511 discloses a composition for paper treatment consisting of at least 35% by weight of a polymerizable compound having a perfluoroalkyl group of 3-20 carbon atoms, 35-60% by weight of vinylidene chloride and 0.5-5% by weight of N-methylolacrylamide or N-methylolmethacrylamide. Also, Japanese Patent Application Kokai (Laid-Open) No. 62-179517 discloses a solid fluoropolymer of water repellency and oil repellency consisting of 40-75% by weight of a perfluoroalkylethyl acrylate monomer, 10-35% by weight of vinylidene chloride and 10-25% by weight of an alkyl acrylate or alkyl methacrylate monomer. Also, Japanese Patent Application Kokoku (Post-Examined) No. 1-58204 discloses a process for producing a fluoroalkyl (meth)acrylate polymer excellent in heat resistance consisting of 70% by weight or more of a fluoroalkyl methacrylate or a fluoroalkyl acrylate and 30% by weight or less of a vinyl monomer.
As the post-treatment method for imparting a particular water repellency agent to a fiber product, it is proposed in, for example, Japanese Patent Application Kokai (laid-Open) No. 59-179876 to form a fluororesin film on the surface of the fiber.
The fiber product subjected to such a post-treatment, however, has a drawback in that the water repellency agent is easily detached by washing or the like.
As the method for treating an acrylonitrile fiber product with said resin, there is ordinarily used a method which comprises spraying a material to be treated, with an aqueous latex of said resin or an organic solvent solution of said resin, or immersing the material to be treated, in a resin solution and subjecting the resulting material to dehydration, etc. to adhere said resin to the material to be treated, and then carrying out drying and heat treatment to form a film of said resin on the surface of the fiber. In this method, however, there easily appear specks caused by the treatment, and increase in the amount of said resin adhered invites a problem in processing. There is also a problem in durabilities of fluorine properties such as washing resistance and the like.
Further, a fluororesin, for example, an ethylene tetrafluoride resin, in particular, is difficult to process by high-pressure extrusion, emulsion shaping, sintering or the like, and is expensive.
In order to solve these problems, the present inventors made extensive study on the structure of polymer per se. As a result, the present inventors developed a completely novel acrylonitrile copolymer and has reached the present invention.
The present inventors made study also on making the novel acrylonitrile copolymer into a fiber. As a result, the present inventors found that a fiber having water repellency permanently or a core-sheath conjugate fiber using the fiber as the sheath component can be obtained, and completed the present invention.
The present invention resides in an acrylonitrile copolymer comprising 70% by weight or more of an acrylonitrile monomer unit and 0.1-30% by weight of a fluoroalkyl methacrylate or fluoroalkyl acrylate monomer unit and having an intrinsic viscosity of 0.8-10.
The present invention further resides in an acrylonitrile fiber prepared from such an acrylonitrile copolymer, or an acrylonitrile type core-sheath conjugate fiber containing such an acrylonitrile copolymer as the sheath component.